@Wingflier
Your title points to the movement being realistic. Aka inertia, acceleration, no max speed but light-speed... there are really valid reasons why those scare people, IMO. Bad gameplay, abuse, difficult to understand, difficult to code, hard on the calculations and scale... all summed up in one word. I think we've all seen games fail at being "space" realistic before. Hence the backlash.
The proposal in the OP points to simply making them a bit more "realistic", as in "having weight", the ships having turning rates, having to actually turn and stuff. (I'm ok with that as far as my opinion is of any value).
I think you scared people here.
About calculation time, really, I hope it's not relevant. Other games handle that just fine and with barely adding micro if any.